A major problem with socks is wear in the heel and toe. Socks made solely of cotton or wool, or of blends of cotton and/or wool with synthetic fibers such as acrylic or polyester rapidly develop holes in the heel and toe. A great advance in durability was made by incorporating nylon in the heel and toe of socks. Although holes in the heel are not now as prevalent, holes in the toe still tend to appear before socks have otherwise outworn their usefulness. This wear may occur as a result of the cutting action, as well as the abrasive action, of the toenails (particularly that of the large toe) pressing the sock against the inside of the shoe.
The more active lifestyle of recent times has increased the demand for improved wear performance in socks. Since no commercially available fiber having an abrasion resistance superior to nylon 6,6 is known, attention was turned to improving cut-resistance.